The present invention is generally directed to a system and method for providing long-term monitoring of uterine activity of an animal. The present invention is more particularly directed to such a system and method wherein a monitor is wearable by a patient and provides long-term monitoring and trending of uterine activity during the prenatal period of a human.
Prolonged pregnancy, generally classified as a gestational age exceeding 42 weeks of gestation, is associated with increased perinatal morbidity and mortality. Specifically, in addition to the increased neonatal deaths, there is an increase in the meconium aspiration, depressed infant at five minutes, and cesarean section rate. The mortality from meconium aspiration can be as high as 38% for those women managed expectantly.
Preterm delivery, or delivery before 37 weeks of gestation, occurs in over 10% of births and also contributes directly to neonatal morbidity and mortality. For infants born between 25 and 30 weeks gestation, the mortality rates are between 10% and 20%. The morbidity of the surviving infants correlates directly with the degree of prematurity. Common problems for the infant include respiratory distress syndrome (RDS) which may require chronic oxygen therapy, intra-ventricular hemorrhage (IVH) which is a harbinger of cerebral palsy, necrotizing enterocolitis (NEC) which can lead to short gut and chronic malnutrition, and patent ductus arteriosus (PDA) which contributes to pulmonary edema and respiratory distress. The incidence of these complications for infants born at 28 and 32 weeks gestation are summarized in Table I below.
TABLE I 28 Weeks 32 Weeks RDS 64% 28% IVH 4% 1% NEC 25% 6% PDA 43% 9%
The incidence of neonatal morbidity can be significantly reduced if a woman with premature labor receives corticosteroid therapy for one to two days prior to delivery. For example, antenatal glucocorticoid treatment decreases the incidence of RDS, with an odds ratio of 0.31. The incidence of pariventricular hemorrhage and NEC are reduced as well. Clearly, premature labor leading to preterm delivery contributes greatly to neonatal morbidity and mortality, and efforts to delay delivery frequently result in an improved neonatal outcome.
Electrical energy applied to the myometrium or uterine muscle has been proposed to inhibit or initiate uterine contractions. One system and method to this end is disclosed in Karsdon, U.S. Pat. Nos. 5,447,526 and 5,713,940 which are incorporated herein by reference. In accordance with a preferred embodiment disclosed in these patents, a first or positive electrode is placed in surface contact to a woman's abdomen over the top of the uterus. Four negative electrodes are placed in spaced apart relation in surface contact to the woman's abdomen over lower portions of the uterus beginning at approximately a mid portion of the uterus. The negative electrodes and the positive electrode are then connected to a muscle controller which generates square wave pulse trains of current between the positive electrode and the negative electrodes. The muscle controller is capable of providing current pulse trains of selectable polarity. The controller is activated to inhibit uterine contractions when they are undesirably present or to initiate uterine contractions when they are undesirably absent.
In accordance with a further embodiment disclosed in the above-referenced Karsdon patents, a uterine contraction monitor is added to the system with feedback to the controller. The amount of electrical energy applied is thus responsive to the sensed contractions. The feedback may be negative or positive depending upon whether contraction initiation or inhibition is desired.
The application of electrical energy to the myometrium as taught in the Karsdon patents is believed to hold great promise in the management of premature labor and prolonged term pregnancies. However, neither of the Karsdon patents addresses the issue of the long-term monitoring of such patients to facilitate a prediction of whether premature labor inhibition or prolonged term pregnancy labor initiation may be required for a patient.